What types of performance do we encourage in our mathematics students? How do these performances reflect students' identity constructions? This paper uses a performance metaphor for identity to analyse interviews with teachers and students in their first year of secondary school. "Perseverance" is valued by teachers, yet many mathematics classrooms appear not to provide the opportunities to persevere and students do not perform identities of perseverance. Rather, "quickness" and "just knowing" the answer are considered part of a successful mathematics identity.